The present invention is directed to ceramic pink-colored materials based on calcium-tin-silicon-chromium oxide and zirconium-titanium-tin-chromium oxide which can be produced without addition of lead compounds.
Pink-colored bodies are employed for the coloration of ceramic glazes as well as for the production of colors for the decoration of stoneware and porcelain. Pink-colored bodies, e.g. of the system calcium-tin-silicon-chromium oxide according to the previous processes of production are only producible as intense red-coloring matter in the presence of lead and alkali compounds, e.g. carbonate or nitrate as mineralizer. The use of these coloring materials or colors producible therefrom on materials which come into contact with food, e.g. stoneware or porcelain vessels, therefore is excluded because of the dangers from the lead in these colors. Boric acid containing lead free pink-coloring material described in the literature [P. Eisbein, Keramische Zeitschrift 23, 214 (1971) and A. Burgyan, Interceram 1, 30, (1979)] are considerably more weakly colored and for that reason are poorly suited for decorative purposes on ceramic products.
Therefore it was the problem of the present invention to develop pink-coloring material for ceramics based on calcium-tin-silicon-chromium oxide or zirconium-titanium-tin-chromium oxide which on the one hand are lead free and on the other are intensely red-colored. Additionally, the material should have a good stability for the broadest possible areas of use, e.g. on porcelain at firing temperatures up to 1300.degree. C.